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Four kinds of industrial solid waste, granulated blast furnace slag (GBFS), electric furnace steel slag (EFSS), semi-dry flue gas desulfurization slag (FGDS) and gypsum were activated by mechanochemistry to prepare a novel kind of cementious material, DA type soil solidification agent (DA agent). Compared to the traditional cementious materials, this paper evaluated DA agent used in silt soil solidification project. Test results showed that DA-4 was prepared with adding the 40% CFBA, 39% GBFS, 11% OPC clinker and 10% gypsum by mill and more superior in material characteristics. It was found that compressive strength of DA-4 paste and mortar specimens at 28-days cured age were 46.0 and 27.3 MPa respectively; 5% of DA-4 was used to stabilize the silt soil in lab and the maximum dry unit weight, optimum moisture content, unconfined compressive strength and CBR value were 1.754 g/cm3, 15.35%, 1.15 MPa and 95.5% respectively. The hardening mechanism of prepared cementious materials is explained by two points: the sulfite or sulfate activation on alkali blast furnace slag; and the hydration product produced from cement clinker hydration process. Besides test programs of the trial pavement section in site showed that stabilized and solidified silt soils by DA-4 can meet the requirement of subgrade of pavement for strength and stiffness.